If you wish to study in Canada, you will need to apply for a study visa. Before you apply for a study visa you will first need to apply to a school and be accepted by that school. Information for study visas is here:
http://www.cic.gc.ca/english/study/study.asp
If you wish to work in Canada, you will need to apply for a work permit. Before you apply for a work permit, you will first have to find an employer in Canada who is willing to offer you a job. Information on work visas is here:
http://www.cic.gc.ca/english/work/apply-how.asp
If you wish to visit Canada (visitors cannot work or attend school), you will need a temporary resident visa. Information is here:
http://www.cic.gc.ca/english/visit/apply-how.asp